Gastrointestinal Tract Gene Expression in Ewes Under Feed Restriction

The gastrointestinal tract is known to adapt itself to changes in feed conditions and is the source of various signals that regulate feed intake and energy homeostasis. Therefore, the objective of this study was to assess the effect of a feed restriction period in the mRNA expression of target genes related to feed intake. The study was conducted in a randomized block design with 5 temporal replications (n = 4 or 3 per treatment and replication) in which thirty-five Rasa Aragonesa ewes (BW=67.1 ± 8.6 kg and BCS=3.0 ± 0.5) were assigned to two nutritional treatments (3.15 vs. 1.05 Mcal per day/1.5 vs. 0.5 times the daily requirements for maintenance; Control and Low, respectively) during 30 days. At the end of this period ewes were slaughtered and a total of 12 samples from abomasum and 12 samples from small intestine (6 ewes per treatment selected by embryo presence) were collected. Relative mRNA expression of glucagon-like peptides 1 and 2 (GLP1, GLP2) and their receptors (GLP1R, GLP2R), neuropeptide Y2 receptor (NPY2R), ghrelin, insulin-like growth factor-1 (IGF1) and its receptor (IGF1R) were determined in abomasum while mRNA expression of IGF1, IGF1R, cholecystokinin (CCK), protein kinase AMP-activated-beta 1 (AMPKB1), neuropeptide Y1 and Y2 receptors (NPY1R, NPY2R), peptide YY (PYY), insulin receptor (INSR) and ghrelin were determined in the small intestine. The mRNA abundance of target genes was assessed by qPCR using SYBR-Green and normalized by the expression of 3 reference genes. Data were analyzed using a mixed model including nutritional treatment as a fixed effect and block as a random effect. Abomasal expression of GLP1 mRNA (1.57 vs. -1.03 ± 0.45; P = 0.004) and GLP2 mRNA (0.25 vs. -1.39 ± 0.37; P = 0.014) were greater in Control than Low ewes. Expression of IGF1R mRNA in small intestine was greater in Control than Low ewes (-2.01 vs. -2.93 ± 0.26; P =0.0375). No other measured genes in abomasum or small intestine showed a differential expression between Control and Low ewes (P>0.05). Results suggest that ewes fed 1.5 times maintenance requirement presented greater expression of genes related to feed intake regulation. The greater expression of IGF1R mRNA in small intestine in these ewes may be associated with greater IGF-1 availability in this tissue, while the greater gene expression of GLP1 and GLP2 mRNA at abomasal tissue need further investigation.